Adjustable rotary sensors for a self-restoring fluidic mortar support system

ABSTRACT

An adjustable tripod support for the firing tube of a mortar is provided with a digital type of fluidic control system responsive to sensing means which detect a predetermined amount of the azimuth and elevation components of the recoil displacement imparted to the tube during firing. In response to such detection, the fluidic control system functions elevation and aziumth pistons which automatically restore the firing tube to the previously selected sighting inclination. The compressed air required by the fluidic control system is stored in an accumulator arranged to be automatically replenished by the discharge gases generated in the mortar tube during the firing thereof. As the firing tube is subjected to recoil displacement, the rotation of a chordally slabbed control shaft associated therewith serves to unblock one of a pair of sensing orifices for activating the control system to provide the required restoration movements of the firing tube. The combination of chordal edges and sensing orifices in each sensing means can be adjusted to provide a given deadband zone through which each control shaft must be rotated before the respective restoration movement is imparted to the firing tube.

United States Patent [191 Ziegler et al.

[ 1 Feb. 18,1975

[ ADJUSTABLE ROTARY SENSORS FOR A SELF-RESTORING FLUIDIC MORTAR SUPPORT SYSTEM [75] Inventors: William H. Ziegler, Waterford; Gary W. Woods, Ballston Lake, both of NY.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: Oct. 15, 1973 [21] Appl. No.: 406,404

Primary Examiner-Stephen C. Bentley Attorney, Agent, or Firm-Eugene E. Stevens, [11; Robert P. Gibson; Natham Edelberg [57] ABSTRACT An adjustable tripod support for the firing tube of a mortar is provided with a digital type of fluidic control system responsive to sensing means which detect a predetermined amount of the azimuth and elevation components of the recoil displacement imparted to the tube during firing. In response to such detection, the fluidic control system functions elevation and aziumth pistons which automatically restore the firing tube to the previously selected sighting inclination. The compressed air required by the fluidic control system is stored in an accumulator arranged to be automatically replenished by the discharge gases generated in the mortar tube during the firing thereof. As the fiting tube is subjected to recoil displacement, the rotation of a chordally slabbed control shaft associated therewith serves to unblock one of a pair of sensing orifices for activating the control system to provide the required restoration movements of the firing tube. The combination of chordal edges and sensing orifices in each sensing means can be adjusted to provide a given deadband zone through which each control shaft must be rotated before the respective restoration movement is imparted to the firing tube.

11 Claims, 9 Drawing Figures PATENTED FEB l 8 I975 SHEET 10F 6 PATENTED FEB] 81975 SHEET U [1F 6 PATENTEU FEB I 8I975 SHEET 5 OF 6 PATENTED FEB 1 8 I975 SHEET 8 0F 6 1 ADJUSTABLE ROTARY SENSORS FOR A SELF-RESTORING FLUIDIC MORTAR SUPPORT SYSTEM BACKGROUND OF THE INVENTION This invention relates to mortars having adjustable support means for aligning the firing tube with a se lected target and is more particularly directed to a mortar support capable of automatically restoring the firing tube to its original targeted position whenever any angular displacement therefrom during firing exceeds a predetermined degree.

In guns such as lightweight infantry type mortars which must be emplaced and sighted with a minimum of effort and time, the delivery of repetitive and accurate fire normally requires frequent manual adjustment of the firing tube support to compensate for the recoil displacements imparted thereto during actual firing especially where the ground on which the mortar isemplaced is of a sandy or similar loose composition. Even where these manual adjustments can be readily made, the resulting interruptions in the continuity of operation of the mortar not only reduce the firepower thereof but frequently have an adverse effect on accuracy. Accordingly, there has recently been developed a tripod mount for a mortar which incorporates a fluidic system of feedback control capable of automatically restoring the firing tube to an established sighting inclination, as more fully disclosed in US. Pat. No. 3,782,243 to William H. Ziegler entitled Automatic Azimuth Recovery System For Cannons.

While the foregoing invention has demonstrated the feasilbility of utilizing fluidic technology to respond to any displacement of a mortar tube away from an established sighting angle and automatically pivot such tube back to its original inclination, the manner in which such return is accomplished does not lend itself to the portability and ease of emplacement required of an in fantry type mortar. For one thing, the fluidic signals produced by any angular displacement of the mortar tube are amplified in an analog fashion thereby requiring a continuous supply of fluid pressure during the actual firing of the mortar as well as during the inoperative intervals between successive firing cycles. Where the fluidic medium is compressed air, the need for a continuous supply of operating pressure has been met by an externally powered compressor unit which introduces logistic problems affecting the mobility and simplicity of operation expected of a lightweight infantry mortar. However, even if the continuous operating pressure required by an analog type of fluidic control system could be satisfactorily supplied from replaceable self-contained cylinders of compressed air, the high precision sensing orifices required for efficient fluidic operation are relatively expensive and prone to frequent malfunction. Furthermore, the cost of these analog systems is substantially increased by the need for air tight connections between the logic elements and the other fluidic components in the system.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a tripod incorporating an improved fluidic control system which can be operated from a self-contained supply of compressed air for adjustably supporting the firing tube of a lightweight infantry mortar at a previously established sighting inclination.

It is another object of this invention to provide a tripod mount, as aforesaid, wherein the supply of compressed air is automatically replenished by the propellant gases generated during each firing of the mortar.

It is also an object of this invention to provide a fluidic control system, as aforesaid, with separate sensing means for individually responding to the azimuth and elevation components of the recoil displacement of the mortar tube during firing.

A further object of this invention lies in the provision of a fluidic control system, as aforesaid, which can be readily adjusted to delay the output thereof untilthe azimuth and elevation components of the displacement imparted to the mortar tube by the recoil forces produced during firing exceed a predetermined angle.

Still another object of this invention is to provide a fluidic control system, as aforesaid, wherein the tolerance between the input and the output of each sensing means is individually adjustable.

Anadditional object of the present invention is the provision of a relatively inexpensive and efficient fluidic system for restoring the firing tube of a mortar to a previously established sighting inclination in a manner which can be readily adjusted in accordance with the extent of the recoil displacement imparted to the mortar tube during firing.

It has been found that the foregoing objects can be attained by substituting a digital or on-off fluidic control circuit for the analog or proportional type described in the aforementioned patent to William H; Ziegler. An appropriate fluidic circuit of this type is more fully disclosed in the copending patent application to William H. Ziegler entitled Digital Fluidic Circuit With Adjustable Time Delay Means for Output C QIlg1Ql; SeI N0. 341,801, filed 16 March 1973. In this particular circuit, any change in the tolerance between the fluidic input and output of the azimuth and elevation sensing means requires replacement of the control shaft with another having a different spacing between the chordal surfaces utilized to block and unblock the sensing orifices. The same result can also be achieved by replacing the housing in which the control shaft is rotatably disposed with another having a different angle between the sensing orifices.

Obviously, these replacements are impractical in an infantry mortar under the conditions normally encountered during the employment thereof in the field. However, in view of the unpredictability of the condition of the ground on which the mortar is emplaced, it is often desirable to vary the tolerance between the input and output, hereafter termed deadband zones." It has been found that this deadband zone can be readily increased or decreased in the particular sensing means responsive to azimuth displacement of the mortar tube simply by providing the control shaft housing with one of the required pair of sensing orifices and locating the other orifice in a separate and adjacent cylindrical member surrounding the control shaft for rotation relative to the housing. Such cylindrical member is releasably secured to the housing for limited rotation in 0pposite directions thereby enabling the angular relationship between the two sensing orifices to be adjusted in accordance with the particular deadband zone desired between the initiation of the recoil displacement of the mortar tube and the fluidic response thereto.

Recoil displacement of the mortar tube in elevation, however, is arranged to be sensed by a control shaft which serves as one of the pair of trunnions utilized to pivotally support the tube. In this control shaft, the sensing orifices are fixed in the housing in which such shaft is rotatably disposed. The desired adjustment of the deadband zone is therefore achieved by a structure wherein the control shaft is divided into adjacent segments each provided with a chordally slabbed surface thereon. One segment is threadably fixed to a slidable sleeve surrounding the mortar tube while the other segment is rotatably seated in the housing containing the sensing orifices and is arranged to be releasably locked to the adjacent segment. Thus, the deadband zone desired between the displacement of the mortar tube in elevation and the fluidic response thereto can be readily achieved by unlocking the rotatable segment for adjustment relative to the fixed segment whereby the chordally slabbed surfaces can then be set to provide a predetermined angle therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS The exact nature of the invention, as well as other objects and advantages thereof, will be readily apparent from consideration of the following specification relating to the annexed drawings wherein:

FIG. 1 is a perspective view of a lightweight mortar supported by a vertically adjustable tripod incorporating a digital type of fluidic control system cabable of automatically maintaining the firing tube of the mortar at a selected sighting inclination, the tripod leg utilized for actual supporting engagement with the firing tube being partially cut away at the lower end thereof to show the actuating piston which serves to pivot the mortar tube in elevation;

FIG. 2 is an enlarged fragmentary front view of the tripod leg which engages the mortar tube showing the components containing the orifices utilized to sense displacement of the mortar tube in azimuth;

FIG. 3 is a section taken along line 3-3 in FIG. 2 to show the relationship between the sensing orifices and the chordal surface of the control shaft prior to the establishment of the desired deadband zone;

FIG. 4 is a view similar to FIG. 3 but showing the change in the relative positions of the sensing orifices and the chordally slabbed surface on the control shaft following the establishment of the desired deadband zone therebetween;

FIG. 5 is an exploded perspective view of the mechanism for sensing recoil displacement of the mortar tube in azimuth;

FIG. 6 is an enlarged fragmentary side view of the connection between the tripod leg and the mortar tube sleeve showing the gear arrangement and indicating means utilized in the attainment of a given deadband zone for the elevation sensing mechanism;

FIG. 7 is a section taken along line 77 in FIG. 6 showing the internal details of the components utilized in adjusting the deadband zone in the elevation sensing mechanism;

FIG. 8 is a section taken along line 8-8 in FIG. 6 showing the actuating piston and the gear arrangement for imparting azimuth movement to the mortar tube; and

FIG. 9 is an exploded perspective view of the mechanism for sensing displacement of the mortar tube in elevation.

DESCRIPTION OF A PREFERRED EMBODIMENT The present invention is applicable to a tripod mount for adjustably supporting a lightweight portable mortar in the manner explained in the first-mentioned patent to William H. Ziegler and provided with a fluidic digital control system of the type shown in the secondmentioned Ziegler application.

Such mount, as best shown in FIG. 1, serves to adjustably support the mortar tube 12 in pivotal engagement with a baseplate 13 and includes a primary leg 14 terminating in a yoke 16 at the upper end thereof in pivotal engagement with the opposite sides of a sleeve 18 which surrounds tube 12 for slidable movement along the length thereof. A pair of secondary legs 20 are pivotally attached to a collar 22 fixed on primary leg 14 in position to cooperate therewith in providing a tripod support for mortar tube 12. One of legs 20 is diametrically enlarged to form an accumulator 24 for storing a supply of compressed air subject to the control of a reg-' ulating valve 26. The air passing through valve 26 is supplied to a fluidic pulse valve 28 mounted on collar 22 and adapted to be triggered by the inertia produced by any recoil displacement of mortar tube 12. Valve 28 is connected by a relatively short conduit 29 to a fluidic control unit 30 which is also mounted on collar 22. A flexible conduit 31 connects the breech end of mortar tube 12 with a check valve 32 at the lower end of accumulator 24 for admitting the propellant gases generated during each firing cycle of the mortar. Suitable filters (not shown) in both check valve 32 and regulator valve 26 remove all impurities in the air being supplied to fluidic control unit 30.

A major portion of tripod primary leg 14 is diametrically enlarged to form a housing 34 which terminates at the upper end thereof in engagement with collar 22. Slidably disposed for telescopic movement in housing 34 is a mating cylinder 36 having a shaft 38 suitably pinned to the underside thereof. A gear mechanism 40 is mounted in the lower end of housing 34 and is arranged to actuate shaft 38 for imparting axial movement to cylinder 36 relative to housing 34. A piston 42 is slidably seated in cylinder 36 and is provided with an upwardly extending rod 44 terminating in a threaded end 46 engageable in a T-shaped coupling 48 depending from yoke 16 and locked thereto by a jam nut 49. As best shown in FIG. 8, coupling 48 includes shoulders 50 at opposite ends thereof for supporting a rod 52 therebetween. Centrally fixed on rod 52 is a cylindrical flange 54 arranged to fit within the hollow interior 56 of a cylindrical neck portion 58 depending from yoke 16. A port 60 on each side of flange 54 provides access to interior 56 for conduits 62 leading to control unit 30. Thus, flange 54 serves as a fixed piston with respect to neck portion 58 of yoke 16 and, consequently, an input of air into interior 56 of cylindrical portion 58 through either port 60 will actuate yoke 16 laterally relative to coupling 48 thereby causing mortar tube 12 to provide about baseplate 13 in an azimuth plane. Shoulders 50 also serve to mount a worm gear 64 which passes through a forward projection 66 on neck portion 58 of yoke 16. A detent plunger 68 is releasably mounted in projection 66 for movement into and out of locking engagement with the threads on worm gear 64. Thus, when plunger 68 is engaged with gear 64, rotation of the latter will impart the same azimuth movement to yoke 16 as that produced by the input of air against piston 54 within neck portion 58.

Rotatably seated in the upper end of cylinder 36 is a cylindrical extension 70 with a diametrically enlarged flange 71 thereon provided with gear teeth 72 substantially flush with the exterior periphery thereof. A worm gear 74 is mounted on a suitable bracket 76 fixed to the exterior of cylinder 36 and is arranged to mesh with gear teeth 72. Extension 70 is provided with a radially extending sensing orifice 80 arranged to communicate with fluidic control unit 30 through a suitable conduit 82. An identical sensing orifice 84, communicating with unit 30 through a conduit 85, is similarly oriented in an adjusting ring 86 secured to extension 70 by a pair of screws 88 terminating in enlarged heads 90. Ring 86 is provided with a pair of diametrically opposed arcuate slots 92 (FIG. 5) therethrough of lesser width than the diameter of screw heads 90. Thus, when tightened, screws 88 prevent rotation of adjusting ring 86 relative to cylinder extension 70. As best shown in FIG. 3, piston rod 44 is chordally slabbed to provide a flat surface 94 which cooperates with the interior peripheries of adjusting ring 86 and cylindrical extension 70 to form an exhaust chamber 96 for the flow of air from control unit 30. As will hereinafter be explained, the relationship between the opposite edges of chordal surface 94 and sensing orifices 80 and 84 establishes a null or deadband zone therebetween through which piston rod 44 can be rotated without initiating a flow of output air from control unit 30 against fixed piston 54.

Yoke 16 is formed with one arm 98 of greater width than the other to accommodate a longer trunnion 100 having a different exterior configuration than the conventional trunnion (not shown) on the opposite side of sleeve 18. In addition, the cylindrical seat for trunnion 100 is diametrically enlarged, as indicated at 102 in FIG. 7, to rotatably receive a bushing 104 provided with alternately disposed channels 106 and O-rings 107 surrounding the exterior periphery thereof. The outer end of bushing 104 is reduced in diameter to form a seat 108 on which a ring gear 110 is fixedly mounted preferably by a press fit thereon. A worm gear 112 extends through yoke arm 98 in meshing engagement with ring gear 110 and is retained in place by a cover 114 coextensive with the exterior periphery of arm 98. Trunnion 100 is divided into separate adjacent segments 116 and 118. One end of segment 116 terminates in a threaded stud 119 (FIG. 9) engageable in sleeve 18 on mortar tube 12 while the opposite end of segment 116 includes a centrally projecting integral pin 120 slotted at the outer end thereof as indicated at 121. Trunnion segment 118 is centrally bored to fit over pin 120 and is also provided with an arcuate slot 122 extending therethrough in parallel relation to the central bore. The outer end of slot 122 is increased in width as shown at 135 to receive the enlarged head of a screw 123 which extends into threaded engagement with trunnion segment 116. Thus, when screw 123 is loosened, segment 118 can be rotated relative to segment 116 to the extent permitted by arcuate slot 122 and then releasably locked in the desired position. The adjacent ends of trunnion segments 116 and 118 are also provided with identical chordally slabbed surfaces, 124 and 125 respectively. As best shown in FIG. 7, surfaces 124 and 125 are disposed in alignment with corresponding sensing orifices 126 and 127 which are, in

turn, in respective communication with the corresponding channels 106 in bushing 104.

A pair of conduits 128 extend from control unit 30 into corresponding ports 129 in yoke arm 98 for passage of control pressure air to channels 166 and thereby to sensing orifices 126 and 127. Thus. when any recoil displacement of mortar tube 12 in elevation rotates trunnion relative to yoke arm 93 to such extent that one edge of either chordal surface 124 or uncovers the corresponding sensing orifice 126 or 127, control pressure air from fluidic unit 30 is permitted to flow into the interior of bushing 1114 and through one of the exhaust openings formed by planar rectangular surfaces 130 and 131 extending from chordal surfaces 124 and 125 respectively. The resulting drop in air pressure by such exhaust flow activates a corresponding logic element in control unit 311 to terminate the operating air pressure directed against one face of actuating piston 42 through a conduit 13 2 passing through an elongated slot 133 circumferentially disposed in the wall of cylinder 36 to communicate with the interior of cylindrical extension 70. Equal operating pressure is arranged to be directed against the opposite face of piston 42 through a conduit 134 passing through a vertically elongated slot 136 in housing 34 arranged to communicate with the interior of cylinder 36. In response to the unequal air pressure on the opposite faces of piston 42, the latter is actuated to impart corresponding axial movement to rod 44 and thereby to yoke 16 which pivots mortar tube 12 about baseplate 13 in the elevational direction required for the restoration thereof to the established sighting inclination.

In order to prepare the mortar for firing, gear mechanism 40 is initially operated to actuate cylinder 36 for raising tube 12 to the desired sighting elevation. There after, detent plunger 68 is pushed inwardly to engage with the threads of worm gear 64 so that manual rotation thereof will shift yoke 16 laterally to position mortar tube 12 in the desired azimuth sighting location. Then worm gear 74 is actuated to rotate cylindrical extension 70 to align an index mark 138 on flange 71 with a corresponding index mark 140 on bracket 76 to establish a zero reference setting wherein sensing orifice 80 is contingent to the edge of chordal surface 94 on piston rod 44, as best shown in FIG. 3. However, if sensing orifice 84 in adjusting ring 86 is similarly positioned in relation to the opposite edge of chordal surface 94, the fluidic control system would be unduly sen sitive since the slightest displacement of mortar tube 12 in azimuth would rotate piston rod 44 to unblock either sensing orifice 811 or 84 and activate a fluidic response thereto. Furthermore, during the restoration of mortar tube 12 to the previously established sighting inclination, considerable difficulty would be encountered in halting the rotation of piston rod 44 simultaneously with the blocking of both sensing orifices 80 and 84- due to the inherent lag between the fluidic response to such blocking and the actual terminationn of the operating pressure air on azimuth actuating piston 54.

It is, therefore, necessary to establish a null or deadband zone between orifice 80 and the corresponding edge of chordal surface 94 which will permit piston rod 44 to be rotated through a given angle prior to actual unblocking of sensing orifice 80. This can be accomplished by providing a series of graduations 141 on the counterclockwise side of index mark 140 spaced apart to provide a reading in terms of the mil" distance utilized in the initial sighting adjustment of mortar tube 12. Thus, cylindrical extension 70 can be rotated by worm gear 74 to position sensing orifice 80 beyond the corresponding edge of chordal surface 94 to the extent necessary to establish a given deadband zone within the limits dictated by the degree of accuracy required of the mortar during firing. Sensing orifice 84 can then be set to establish an equivalent deadband zone simply by loosening screws 88 and rotating adjusting ring 86 to relocate sensing orifice 84 to the same distance beyond the corresponding edge of chordal surface 94 as sensing orifice 80. A zero reference setting for adjusting ring 86 caribeest'ablis'hed by the alignment'of an index" mark 142 thereon with a corresponding index mark 144 at the upper end of cylindrical extension 70 which is, in turn, located in vertical alignment with index mark 138 on flange 71 thereof. In order to determine the amount of rotational adjustment required by ring 86, a series ofmil graduation 146 are located on the clockwise side of index mark 144. While the extent .of these deadband zones depends on the rigidity of the ground on which the mortar is emplaced, they should generally be large enough to prevent shuttling of the mortar tube in response to the tendency-for rotating piston rod 44 to coast to a halt during the fluidic lag between the termination of the sensing signal and the termination of the system output pressure. At the same time, these deadband zones should not be larger than the allowable sighting error which can be tolerated by the particular degree of firing accuracy desired of the mortar.

The deadband zones involved in the elevational sensing mechanism are similarly adjustable to provide a predetermined level below which recoil displacement of tube 12 will not initiate the fluidic response which serves to restore the tube to itsoriginal sighting inclination. In order to permit the necessary adjustment, cover 1 14 is fabricated of a suitable transparent material and an arcuate indicator 150 graduated in degrees is adjustably retained in a corresponding track 151 in outer face of yoke arm 98. Indicator 150 is provided with an outwardly projecting thumbpiece 152 extending beyond the periphery of yoke arm 98 to enable manual adjustment thereof within track 151. Retention of indicator 150 against premature displacement is accomplished by the frictional contact therewith of a rubbertipped screw 153 (FIG. 6) threadably engaged in the transparent material of cover 114. An index mark 154 is inscribed across the outer end face of bushing 104 in fixed alignment with a corresponding index mark 155 on ring gear 110. Index mark 155 is arranged to align with the graduations on indicator 150 while index mark 154 is arranged for alignment with a corresponding mark 156 on the outer end face of trunnion segment 118. On either side of index mark 156 are provided mil graduations 158 in adjacent relation to an index mark 160 extending along the portion of pin 120 projecting beyond the end face of segment 118. During the assembly of the elevational sensing mechanism, trunnion segment 118 was locked to segment 116 by screw 123 with index mark 156 in alignment with idex mark 160 on pin 120 thereby orienting chordal surfaces 124 and 125 at the particular included angle which will provide a zero deadband setting relative to sensing orifices 126 and 127 when index mark 156 is in alignment with index mark 154 on bushing 104.

Once the azimuth sensing mechanism has been set to provide the desired deadband zone which will be compatible with the condition of the ground on which the tripod and baseplate of the mortar are supported, the elevational sensing mechanism can then be similarly adjusted. Since the elevation of mortar tube 12 caused trunnion to be rotated relative to bushing 104, worm gear 112 must first be actuated to restore bushing 104 to the rotated position in which index mark 154 thereon is again aligned with index mark 156 and thereby with index mark 160 on trunnion segment 116 for positioning sensing orifices 126 and 127 adjacent the correspondingremote edges of'chordal surfaces 124 and 125. Then, once screw 123 is loosened, trunnion segment 118 is rotated in the direction desired until index mark 160 on pin 120 is in alignment with the particular one of the mil graduations 158 which represents twice the deadband zone actually desired. Such doubling of the deadband zone between the edge of chordal surface and sensing orifice 126 antici-' pates the subsequent equalization of both deadband zones as trunnion 100 is rotated during the first restoration of mortar tube 12 to the original sighting inclination thereof. It should be noted that this adjustment to a particular deadband zone could have been eliminated if the condition of the ground on which the mortar was to be fired were known in advance. Such knowledge would, of course, permit the desired deadband zone to be set prior to emplacement of the mortar tripod.

Once the desired deadband zone has been set, screw 153 is loosened and indicator adjusted to cooperate with index mark on worm gear 110 and provide a reading indicative of the angle of elevation to which mortar tube 12 was sighted. Thus, in the event it becomes necessary to change the elevation setting of mortar tube 12, this can be accomplished within the need for adjusting trunnion segment 118 to maintain the desired deadband zones. If, for example, it is desired to elevate mortar tube 12 another 5, worm gear 112 is rotated until index mark 155 on work gear 110 is brought into alignment with the corresponding angle graduation on indicator 150. Then, puls'evalve 28 is manually triggered to activate fluidic control unit 30 for effecting a flow of air to sensing orifices 126 and 127. The new positions of sensing orifices 126 and 127 relative to the adjacent edges of chordal surfaces 124 and 125 will cause fluidic control unit 30 to actuate piston rod 44 for imparting elevational movement to mortar tube 12 until the corresponding rotation of trunnion 100 once again blocks sensing orifices 126 and 127 in bushing 104 within the established deadband zone and realigns index mark 156 with index mark 154 on bushing 104.

When the mortar is fired, any movement which may be imparted to baseplate 13 by the recoil forces produced during firing causes a corresponding change in the angle of inclination of firing tube 12. In the event the azimuth component of such inclination of mortar tube 12 rotates piston rod 44 so that the edge of surface 94 passes through the corresponding deadband zone to unblock one of the pair of sensing orifices 80 and 84, fluidic control unit 30 is activated to apply operating air pressure against the corresponding end of piston 54 thereby pivoting mortar tube 12 back to the previous angle of inclination in the azimuth plane. These restoration movements of mortar tube 12 will continue to take place as long as neck portion 58 on yoke 16 has not reached either of shoulders 50 on the T-shaped coupling 48 in threaded engagement with the upper end of piston rod 44. Similarly, when the fore and aft component of the recoil displacement of baseplate 13 rotates trunnion 100 so that one edge of chordal surface 124 or 125 passes through the corresponding deadband zone to block one of sensing orifices 126 and 127, fluidic control unit 30 is activated to apply operating pressure against the corresponding end of piston 42 thereby pivoting mortar tube 12 back to the previous angle of inclination thereof.

Thus, there is here provided a self-adjusting tripod mount for a mortar capable of automatically restoring the firing tube to a previously established sighting inclination in both azimuth and elevation with far greater responsiveness and rapidity than heretofore possible. Furthermore, the type of digital fluidic control system here incorporated in the tripod mount makes it possible to utilize a self-contained supply of compressed air whose weight and bulk does not interfere with the portability and simplicity of operation required of an infantry type mortar. Additionally, inasmuch as each firing of the mortar produces expanding discharge gases, a portion thereof will flow through check valve 32 into accumulator 24 to automatically replenish the supply of compressed air therein. Thus, the size of accumulator 24 may be reduced to store only the small quantity of compressed air required to check the response of the fluidic system to manual displacements of the firing tube during the initial adjustment of the deadband zones in each direction of firing tube movement.

Another important feature of the present invention lies in the flexibility with which the deadband zones in both the azimuth and elevation sensing mechanisms can be adjusted. For example, it is possible to tailor the responsiveness of the fluidic system to the actual recoil displacements of the firing tube in accordance with the composition of the ground on which the baseplate and the tripod mount are supported. Where the ground is soft, the deadband zones involved in the response of the fluidic control to recoil displacement of the firing tube may be increased and where the ground is hard the deadband zones may be correspondingly decreased. Also, these deadband zones may be adjusted to conform with the dimensional tolerances of the component parts of the sensing mechanisms.

The foregoing disclosure and description of the invention is illustrative only. Various changes may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim:

1. In an adjustable tripod support for the firing tube of a mortar having a fluidic control system for automatically restoring the tube to a previously selected sighting inclination in response to the recoil displacement encountered during the firing thereof, the combination of,

a primary leg having a yoke in pivotal supporting engagement with the firing tube,

a pair of secondary legs pivotally engageable with said primary leg for supporting the firing tube at the selected sighting inclination,

a first piston having an elongated rod extending therefrom into fixed engagement with said yoke and slidably disposed in said primary leg for imparting elevational movement to the firing tube,

a second piston slidably disposed in said yoke for imparting azimuth movement to the firing tube,

first sensing means disposed in said yoke and responsive to the elevational component of the recoil displacement of the firing tube for activating the fluidic control system to actuate said first piston until the firing tube is restored to the initial sighting inclination thereof, said first sensing means comprismg,

a control shaft rotatably disposed in said yoke with one end fixed to the firing tube and the opposite end thereof having a separately rotatable segment thereon,

said shaft and said segment each having a transverse chordal surface disposed in adjacent relation and extending in opposite directions to form an angle therebetween,

a cylindrical bushing rotatably disposed in said yoke in surrounding relation to'said chordal surfaces, said bushing having a pair of sensing orifices through opposite sides thereof in coaxial relation and in respective alignment with said chordal surfaces, and

means for releasably locking said rotatable segment to said control shaft with the remote edges of said chordal surfaces selectively positioned relative to said sensing orifices to establish a desired deadband zone through which said control shaft must be rotated prior to unblocking one of said orifices for activating the fluidic control system to actuate said first piston,

second sensing means disposed in said primary leg in surrounding relation to said primary leg and responsive to the azimuth component of the recoil displacement of the firing tube for activating the fluidic control system to actuate said second piston until the firing tube is restored to the initial sighting inclination thereof, and means for adjusting said first and second sensing means to delay activation of the fluidic control system until the recoil exceeds a predetermined degree of movement in azimuth and elevation, respectively.

2. The tripod support defined in claim 1 including,

first index means on said control shaft for indicating the established deadband zone between said chordal surfaces and said respective sensing orifices, and

second index means on said bushing and said yoke for indicating the angular relationship between said deadband zone and the sighting inclination of the firing tube in elevation.

3. The tripod support defined in claim 1 wherein said second sensing means comprises,

a chordal surface extending longitudinally along said piston rod to form opposite edges thereon,

a cylindrical extension rotatably disposed on said primary leg in surrounding relation to said chordal surface,

an adjusting ring coextensive with said cylindrical extension and rotatably disposed in adjacent relation thereto,

said ring and said extension each having a radiall disposed sensing orifice spaced apart to a greater extent than said opposite edges of said chordal surface, and

means for releasably locking said ring to said exten-' sion with said orifices selectively positioned relative to said opposite edges of said chordal surface to establish a desired deadband zone through which said piston rod must be rotated prior to unblocking one of said orifices for activating the fluidic control system to actuate said second piston.

4. The tripod support defined in claim 3 including,

first index means on said cylindrical extension and said adjusting ring for indicating the established deadband zone between said orifices and said edges of said chordal surface, and

second index means on said extension and said primary leg for indicating the angular relationship between said deadband zone and the sighting inclination of the firing tube in azimuth.

5. The adjustable tripod support defined in claim 1 including,

an accumulator on one of said secondary legs for storing a supply of compressed air for use by the fluidic control system,

conduit means between the firing tube and said accumulator for passage therein of the discharge gases generated during each firing of the mortar to replenish the supply of air in said accumulator, and

conduit means between said accumulator and the firing control system for passage of the air released from said accumulator.

6. In an adjustable tripod for supporting the firing tube of a mortar in a selected sighting inclination, said tripod including a fluidic control system for automatically restoring the firing tube to the selected sighting inclination thereof in response to the recoil displace ment encountered during firing, means for varying the degree of recoil displacement required to activate the fluidic control system for actuating the firing tube in elevation, comprising,

a sleeve slidably engageable with the firing tube,

a pair of trunnions projecting from opposite sides of said sleeve,

a primary tripod leg having a yoke in pivotal engagement with said trunnions,

a segment rotatably supported on the outer end of one of said trunnions,

a pair of chordal surfaces extending respectively across said one trunnion and said segment in adjacent relation to each other and in opposiste directions to form an angle therebetween,

a cylindrical bushing rotatably disposed in said yoke to surround said one trunnion and ,having a pair of radially extending orifices therethrough disposed in respective alignment with each of said chordal surfaces, and

means for releasably locking said rotatable segment to said one trunnion with the remote edges of said chordal surfaces selectively positioned relative to said sensing orifices to establish a desired deadband zone through which said one trunnion must be rotated prior to unblocking one of said orifices for activating the fluidic control system to impart restoration movements to the firing tube in elevation.

7. The adjustable tripod defined in claim 6 wherein a pin extends centrally outward from said one trunnion through said segment to project therefrom, said segment having an arcuate slot of stepped width extending longitudinally therethrough, and said means for releasably locking said segment to said one trunnion comprises a screw having an enlarged head receivable in the larger width portion of said arcuate slot and a body extending therethrough into threaded engagement with said one trunnion whereby said chordal surface on said segment is disposed for limited rotation relative to said corresponding orifice in said bushing when said screw is loosened.

8. The adjustable tripod defined in claim 7 including,

a first index mark on the portion of said pin projecting from said segment,

a plurality of graduations on the outer end of said rotatable segment disposed for cooperating alignment with said first index mark to indicate the angle between said chordal surfaces in terms of the sighting inclination of the firing tube,

a second index mark on the outer end of said cylindrical bushing,

a plurality of graduations on said yoke for cooperating with said second index mark to indicate the degree of any change in the sighting inclination of the firing tube in elevation, and

gear means for rotating said cylindrical bushing to realign said second index with said graduations on said rotatable segment and thereby reestablish the desired deadband zone in the event of any change in the sighting inclination of the firing tube in elevation.

9. In an adjustable tripod for supporting the firing tube of a mortar in a selected sighting inclination, said tripod including a fluidic control system for automatically restoring the firing tube to te selected sighting inclination thereof in response to the recoil displacement encountered during firing, means for varying the degree of recoil displacement required to activate the fluidic control system for actuating the firing tube in azimuth, comprising,

a sleeve slidably engageable with the firing tube,

a pair of trunnions projecting from opposite sides of said sleeve,

a primary tripod leg having a slidablel piston rod therein terminating in a yoke pivotally engageable with said trunnions,

a chordal surface extending longitudinally along said piston rod to form opposed edges thereon,

a cylindrical extension rotatably secured to said primary leg in surrounding relation to said chordal surface,

an adjusting ring coextensive with said cylindrical extension and rotatably disposed in adjacent relation thereto,

said ring and said extension each having a radially disposed'sensing orifice spaced apart to a greater extent than said opposite edges of said chordal surface, and

means for releasably locking said ring to said extension with said orifices selectively positioned relative to said opposite edges of said chordal surface to establish a desired deadband zone through which said piston rod must be rotated prior to unblocking one of said orifices for activating the fiuidic control system to impart restoration movement to the firing tube in azimuth.

l0. The'adjustable tripod defined in claim 9 wherein said adjusting ring is provided with a pair of oppositely disposed arcuate slots therethrough and said means for releasably locking said ring to said extension comprises a pair of screws having enlarged heads and body portions extending respectively through said arcuate slots into threaded engagement with said cylindrical extension whereby said orifice in said adjusting ring is disposed for limited rotation relative to said corresponding edge on said chordal surface when said screws are loosened.

11. The adjustable tripod defined in claim 9 including,

a first index mark on said adjusting ring, a second index mark on said cylindrical extension, a plurality of graduations on one side of said second index mark disposed for cooperating alignment with said first index mark to indicate the angle between said sensing orifices in terms of the sighting inclination of the firing tube,

a third index mark on said cylindrical extension in alignment with said second index mark thereon,

a fourth index mark on said primary tripod leg,

a plurality of graduations on one side of said fourth index mark for cooperating with said third index mark to indicate said deadband zone between said orifices and said opposed edges of said chordal surface in terms of the sighting inclination of the firing tube in azimuth, and

gear means for rotating said cylindrical extension to realign said third index mark with said fourth index mark and thereby reestablish said deadband zone in the event of any change in the sighting inclina tion of the firing tube in azimuth. 

1. In an adjustable tripod support for the firing tube of a mortar having a fluidic control system for automatically restoring the tube to a previously selected sighting inclination in response to the recoil displacement encountered during the firing thereof, the combination of, a primary leg having a yoke in pivotal supporting engagement with the firing tube, a pair of secondary legs pivotally engageable with said primary leg for supporting the firing tube at the selected sighting inclination, a first piston having an elongated rod extending therefrom into fixed engagement with said yoke and slidably disposed in said primary leg for imparting elevational movement to the firing tube, a second piston slidably disposed in said yoke for imparting azimuth movement to the firing tube, first sensing means disposed in said yoke and responsive to the elevational component of the recoil displacement of the firing tube for activating the fluidic control system to actuate said first piston until the firing tube is restored to the initial sighting inclination thereof, said first sensing means comprising, a control shaft rotatably disposed in said yoke with one end fixed to the firing tube and the opposite end thereof having a separately rotatable segment thereon, said shaft and said segment each having a transverse chordal surface disposed in adjacent relation and extending in opposite directions to form an angle therebetween, a cylindrical bushing rotatably disposed in said yoke in surrounding relation to said chordal surfaces, said bushing having a pair of sensing orifices through opposite sides thereof in coaxial relation and in respective alignment with said chordal surfaces, and means for releasably locking said rotatable segment to said control shaft with the remote edges of said chordal surfaces selectively positioned relative to said sensing orifices to establish a desired deadband zone through which said control shaft must be rotated prior to unblocking one of said orifices for activating the fluidic control system to actuate said first piston, second sensing means disposed in said primary leg in surrounding relation to said primary leg and responsive to the azimuth component of the recoil displacement of the firing tube for activating the fluidic control system to actuate said second piston until the firing tube is restored to the initial sighting inclination thereof, and means for adjusting said first and second sensing means to delay activation of the fluidic control system until the recoil exceeds a predetermined degree of movement in azimuth and elevation, respectively.
 2. The tripod support defined in claim 1 including, first index means on said control shaft for indicating the established deadband zone between said chordal surfaces and said respective sensing orifices, and second index means on said bushing and said yoke for indicating the angular relationship between said deadband zone and the sighting inclination of the firing tube in elevation.
 3. The tripod support defined in claim 1 wherein said second sensing means comprises, a chordal surface extending longitudinally along said piston rod to form opposite edges thereon, a cylindrical extension rotatably disposed on said primary leg in surrounding relation to said chordal surface, an adjusting ring coextensive with said cylindrical extension and rotatably disposed in adjacent relation thereto, said ring and said extension each having a radially disposed sensing orifice spaced apart to a greater extent than said opposite edges of said chordal surface, and means for releasably locking said ring to said extension with said orifices selectively positioned relative to said oppOsite edges of said chordal surface to establish a desired deadband zone through which said piston rod must be rotated prior to unblocking one of said orifices for activating the fluidic control system to actuate said second piston.
 4. The tripod support defined in claim 3 including, first index means on said cylindrical extension and said adjusting ring for indicating the established deadband zone between said orifices and said edges of said chordal surface, and second index means on said extension and said primary leg for indicating the angular relationship between said deadband zone and the sighting inclination of the firing tube in azimuth.
 5. The adjustable tripod support defined in claim 1 including, an accumulator on one of said secondary legs for storing a supply of compressed air for use by the fluidic control system, conduit means between the firing tube and said accumulator for passage therein of the discharge gases generated during each firing of the mortar to replenish the supply of air in said accumulator, and conduit means between said accumulator and the firing control system for passage of the air released from said accumulator.
 6. In an adjustable tripod for supporting the firing tube of a mortar in a selected sighting inclination, said tripod including a fluidic control system for automatically restoring the firing tube to the selected sighting inclination thereof in response to the recoil displacement encountered during firing, means for varying the degree of recoil displacement required to activate the fluidic control system for actuating the firing tube in elevation, comprising, a sleeve slidably engageable with the firing tube, a pair of trunnions projecting from opposite sides of said sleeve, a primary tripod leg having a yoke in pivotal engagement with said trunnions, a segment rotatably supported on the outer end of one of said trunnions, a pair of chordal surfaces extending respectively across said one trunnion and said segment in adjacent relation to each other and in opposiste directions to form an angle therebetween, a cylindrical bushing rotatably disposed in said yoke to surround said one trunnion and having a pair of radially extending orifices therethrough disposed in respective alignment with each of said chordal surfaces, and means for releasably locking said rotatable segment to said one trunnion with the remote edges of said chordal surfaces selectively positioned relative to said sensing orifices to establish a desired deadband zone through which said one trunnion must be rotated prior to unblocking one of said orifices for activating the fluidic control system to impart restoration movements to the firing tube in elevation.
 7. The adjustable tripod defined in claim 6 wherein a pin extends centrally outward from said one trunnion through said segment to project therefrom, said segment having an arcuate slot of stepped width extending longitudinally therethrough, and said means for releasably locking said segment to said one trunnion comprises a screw having an enlarged head receivable in the larger width portion of said arcuate slot and a body extending therethrough into threaded engagement with said one trunnion whereby said chordal surface on said segment is disposed for limited rotation relative to said corresponding orifice in said bushing when said screw is loosened.
 8. The adjustable tripod defined in claim 7 including, a first index mark on the portion of said pin projecting from said segment, a plurality of graduations on the outer end of said rotatable segment disposed for cooperating alignment with said first index mark to indicate the angle between said chordal surfaces in terms of the sighting inclination of the firing tube, a second index mark on the outer end of said cylindrical bushing, a plurality of graduations on said yoke for cooperating with said second index mark to indicate the degree of any change in the sighting inclinaTion of the firing tube in elevation, and gear means for rotating said cylindrical bushing to realign said second index with said graduations on said rotatable segment and thereby reestablish the desired deadband zone in the event of any change in the sighting inclination of the firing tube in elevation.
 9. In an adjustable tripod for supporting the firing tube of a mortar in a selected sighting inclination, said tripod including a fluidic control system for automatically restoring the firing tube to te selected sighting inclination thereof in response to the recoil displacement encountered during firing, means for varying the degree of recoil displacement required to activate the fluidic control system for actuating the firing tube in azimuth, comprising, a sleeve slidably engageable with the firing tube, a pair of trunnions projecting from opposite sides of said sleeve, a primary tripod leg having a slidablel piston rod therein terminating in a yoke pivotally engageable with said trunnions, a chordal surface extending longitudinally along said piston rod to form opposed edges thereon, a cylindrical extension rotatably secured to said primary leg in surrounding relation to said chordal surface, an adjusting ring coextensive with said cylindrical extension and rotatably disposed in adjacent relation thereto, said ring and said extension each having a radially disposed sensing orifice spaced apart to a greater extent than said opposite edges of said chordal surface, and means for releasably locking said ring to said extension with said orifices selectively positioned relative to said opposite edges of said chordal surface to establish a desired deadband zone through which said piston rod must be rotated prior to unblocking one of said orifices for activating the fluidic control system to impart restoration movement to the firing tube in azimuth.
 10. The adjustable tripod defined in claim 9 wherein said adjusting ring is provided with a pair of oppositely disposed arcuate slots therethrough and said means for releasably locking said ring to said extension comprises a pair of screws having enlarged heads and body portions extending respectively through said arcuate slots into threaded engagement with said cylindrical extension whereby said orifice in said adjusting ring is disposed for limited rotation relative to said corresponding edge on said chordal surface when said screws are loosened.
 11. The adjustable tripod defined in claim 9 including, a first index mark on said adjusting ring, a second index mark on said cylindrical extension, a plurality of graduations on one side of said second index mark disposed for cooperating alignment with said first index mark to indicate the angle between said sensing orifices in terms of the sighting inclination of the firing tube, a third index mark on said cylindrical extension in alignment with said second index mark thereon, a fourth index mark on said primary tripod leg, a plurality of graduations on one side of said fourth index mark for cooperating with said third index mark to indicate said deadband zone between said orifices and said opposed edges of said chordal surface in terms of the sighting inclination of the firing tube in azimuth, and gear means for rotating said cylindrical extension to realign said third index mark with said fourth index mark and thereby reestablish said deadband zone in the event of any change in the sighting inclination of the firing tube in azimuth. 